Combination extraction-demetalation process for heavy oils



United States Patent 0 3,389,912 COMBINATTUN EXTRACTlQN-DEMETALATKGNPRQCESS FOR HEAVY OILS Norman J. Paterson, San Rafael, Califi, assignorto {Shevron Research Company, San Francisco, Qalifi, a corporation ofDelaware Fiied Mar. 1, 1967, Ser. No. 619,772 4 Claims. (Cl. 208-86)ABSTRACT OF THE DISCLGSURE A process for the production of a low metalcontent, relatively parafiinic cracking stock and a relatively aromaticstock from which pitch binder oil and carbon black oil may be produced.Asphalt, naphthenic and aromatic oils and solvents from a lubricatingoil extraction process are contacted with a deasphaltenedmetal-containing oil to form a more parafiinic oil and a more aromaticfrac tion. The latter fraction is visbroken and vacuum pitch stripped.Asphaltenes and pitch stripper bottoms are converted to hydrogen bypartial oxidation.

Background of the invention This invention relates to processes fordemetallizing residual oil. More particularly, it relates to processesfor producing a low metal content feed of increased parafiinicitysuitable for catalytic cracking.

It has heretofore been known that oils having a relatively high contentof polynuclear aromatic hydrocarbons are less suitable for cracking thannonaromatic oils since cracking of aromatic-containing oils results in agreater degradation of the oil into undesired products, such as coke andgas, for a given conversion to gasoline than cracking of nonaromaticoils. Thus the ratio of gasoline to coke or gas for a given conversionis higher when cracking nonaromatic oils than when cracking aromaticoils. In view of the foregoing, it has been proposed to remove aromaticconstituents from aromatic charge oil before subjecting the same tocracking. Removal of aromatic constituents may be accomplished bytreatment of the cracking charge stock with a solvent having a selectivesolvent power for aromatics as compared with nonaromatics. Such proposedtreatment, however, has been relatively expensive due to the necessityfor recovering solvent and, accordingly, has not been widely practicedin commercial operation since the improved cracking characteristics ofthe stock so treated have ordinarily not ofiset the additionaloperational costs involved.

in catalytic cracking, it has also been known for some time that certainmetals-in particular, iron, nickel and vanadiumare very harmful tocracking catalysts. Deposition on cracking catalysts of concentrationsof about 0.1 weight percent or less of such metals causes the productionof excessive amounts of coke and gas at the expense of valuable gasolineand heating oil fractions. This leads to an overloading of theregeneration and gas handling equipment and reduces the allowable feedrate to the catalytic cracking units.

There are two principal sources of metallic contamination in catalyticcracking units. The first is erosion of the unit itself. The secondsource is unfilterable metailic impurities brought in with thefeedstock, either in colloidal suspension or particularly as oilsoluble,metallo-organic compounds. It is the removal of this latter type ofcontaminants with which the present invention is particularly concerned.

It has also been known, prior to the present invention, to improve thequalities of petroleum lubricating oil fractions by extraction with afirst solvent having a preferential selectivity for the relatively morearomatic and naphthenic type constituents as compared to the relativelymore parafiinic type constituents. In such prior practice, the usualprocedure for solvent refining of lubricating oils has been to contactthe oil stock undergoing treatment with solvent in an extraction tower.Thus the oil charge is ordinarily introduced into a lower portion of anelongated tower While solvent is introduced into the upper portionthereof. The oil and solvent move countercurrently through the tower,eflicient contact between the countercurrently moving phases beinggenerally secured by suitable distributing and contacting meanssuch asby contact masses, distributing plates, pierced plates, rotating disccontactors, and the like. Temperature and pressure conditions aremaintained in the tower to secure the formation of extract and raftinatephases. The phases are separately removed from the tower. Solvents ofthe class which is suitable for this extractive operation are, forexample, 'furfural, sulfur dioxide, phenol, cresol, aniline,nitrobenzene, beta-beta-dichloroethyl ether (chlorex), and the like.Such solvents may have been further modified with regard to selectivityand solvent power by the addition of, for example, water, alcohols, orglycols. The preferred solvents are phenol and furfural.

In many cases, particularly when a lubricating oil fraction containsvery heavy naphthenic or aromatic and asphaltic components, it isdesirable to add a second solvent, normally a light parafiin, to aid inseparating the two phases. This solvent causes the heavier materials tobe rejected into the extract phase, while the solvent is concentrated inthe raflinate phase which contains the high-quality lubricating oil.

The products of the treatment of such a lubricating oil fraction withtwo or more solvents are these: (1) a lubrieating oil extract which, asthe term will hereinafter be used, is defined as the lowerviscosity-gravity constant phase of the two phases produced andcomprises the major portion of the first (selective) solvent, the minorportion of the second (paraffinic) solvent, and the heavier aromatic andnaphthenic components of the lubricating oil fraction; and (2) theratfinate, or higher viscositygravity constant phase of the two phasesproduced, which comprises the more paraflinic components of thelubricating oil feedstock, the minor portion of the first solvent, andthe major portion of the second solvent.

It has also been known that the lubricating oil extract can be employeddirectly without removal of either solvent in the extraction of apetroleum oil to be used as a cracking charge stock. The extract andraflinate fractions obtained from this extraction are thereafterseparated and the solvents are removed therefrom. The resultingsolvent-free railinate fraction can then be subjected to catalyticcracking, affording a high yield of a product characterized by animproved gasoline/ coke ratio.

Summary It has now been discovered that if the lubricating oil extractcontains a substantial amount of asphalt as well as the other componentsdescribed above, this asphaltic extract may be used to demetallize ametals-containing petroleum oil while simultaneously separating from thepetroleum oil a predominantly more parafiinic catalytic cracking stock.

In broad outline, this invention involves three processing zones and twofeedstocks. The first feedstock, which is the metalsandasphaltene-containing petroleum oil boiling substantially entirely above900 P. which is to be processed, is passed into a deasphaltening zonewherein it is contacted with a C -C paraflinic solvent and separatedinto two fractions. The heavier or asphaltene fraction comprisesasphaltenes with a softening point above 300 F. (as measured by theball-and-ring method of ASTM D36-26) containing a portion of themetalliferous contaminants and a minor portion of the parafiinicsolvent. The lighter or maltene fraction comprises nonasphaltenematerials and the remainder of the metalliferous contaminants.Designation of at least a 300 F. softening point for the heavier phaseassures that essentially all the nonasphaltene :material will be in thelighter phase. The asphaltene fraction is withdrawn from the deasphaltening zone and may be further processed in a manner to behereinafter described. The maltene fraction is also withdrawn from thedeasphaltening zone and is passed into the central processing zone,which is the first extraction zone, wherein it is contacted with asphaltand other materials also hereinafter described.

The second, or asphaltic, feedstock is a partially naphthenic andaromatic lubricating oil fraction. This feedstock usually differs fromthe first feedstock in that it is a preferred feedstock for theproduction of lubricating oils. In addition, it generally contains ahigher proportion of components boiling within the range of from about650-1,100 F. and has a lower metal content. This feedstock is contactedin a second extraction zone with at least one solvent substantiallyselective for the extraction of naphthenic and aromatic components fromthe feedstock and at least one solvent which preferentially concentratesin the lighter phase and rejects asphaltic components into the heavierphase upon phase separation in this zone. The heavier phase is theasphaltie extract described hereinbefore. This asphaltic extract iswithdrawn from this second extraction zone and passed into the firstextraction zone wherein it contacts the maltene fraction from thedeasphaltening zone. The asphalt and other components, including thesolvents, in the asphaltic extract serve to cause separation of the materials in the first extraction zone into a lower specific gravity, lowermetal content, more paraffinic fraction and a higher specific gravity,higher metal content, more aromatic fraction. The lighter fractioncontains less than 25 p.p.m. metals (calculated as elemental metal) andmay be used as a hydrocracker charge stock. Preferentially it willcontain less than 1 p.p.m. metals and may be used as a catalyticcracking charge stock. These fractions are separately removed from thefirst extraction zone, and the solvents are removed from each.

In a narrower form, the invention comprises the steps recited abovefollowed by thermal visbreaking of the solvent-free, more aromaticfraction at a temperature in the range of from about 650 F. to about1,000" P. and a pressure in the range of from about 50 to about 1,000p.s.i.g. This increases the aromaticity of the more aromatic fractionand enhances its ability to produce highquality carbon black oil andpitch binder base stock in subsequent processing steps.

In a still narrower form, the invention comprises the above stepsfollowed by fractionation of the visbroken material into at least alighter fraction and a heavier, more aromatic fraction followed bystripping of at least a portion of the latter with steam in a vacuumpitch stripping zone to produce a high-quality carbon black oil andpitch binder base stock.

In a still narrower form, the invention comprises the above stepsfollowed by conversion of at least a portion of the heavier fractionfrom the vacuum pitch stripping zone and the asphaltene fraction fromthe deasphaltening zone to hydrogen by reacting in the presence ofoxygen in a partial oxidation zone comprising at least a gas generator,a shift converter and carbon dioxide removal means. The hydrogen soproduced can be used in the hydrogen-consuming units in the refiningsystem, thereby making the system for processing the various oilfractions here produced at least partially self-sutficient.

Brief description of the drawings FIGURE 1 illustrates the process ofthis invention in its both broadest form and successively narrowerembodiments; and

FIGURE 2 illustrates the embodiment of the example which will bepresented hereinafter and shows how the process of this invention may beincorporated into an overall refining scheme.

Description of the preferred embodiments FIGURE 1 illustrates theprocess of this invention in its broadest form. A petroleum feedstock,which may be a crude oil, shale oil, topped crude or similar material,enters through line 1 to first crude unit 2 wherein it is fractionatedinto a plurality of materials of increasing boiling point. The lightestof these materials is removed through line 3, and successively higherboiling and heavier materials are removed through lines 4, 5 and 6. Theremaining materials which boil above 900 F. are withdrawn from thebottom of first crude unit 2 through line 7 and are passed intodeasphaltening zone 8 wherein they are contacted with a C -C parafiinicsolvent which enters deasphaltening zone 8 through line 9. A detaileddescription of deasphaltening zone 8, as well as a detailed descriptionof the other processing zones, will be presented hereinafter.

In deasphaltening zone 8, the 900 F.+ bottoms material is separated intotwo fractions on contact with the paraffinic solvent. The asphaltenefraction is withdrawn through line 10 for further processing hereinafterdescribed. The maltene fraction, which may include the major portion ofthe parafiinic solvent, is withdrawn through line 11 and passed to firstextraction zone 12.

A second feedstock, which must contain asphalt and other naphtheniccomponents, enters second crude unit 13 through line 14. This feedstockis fractionated to remove the light components in a manner similar tothat described for first crude unit 2. The lightest material is takenoff overhead through line 15, and successively higher and heavierboiling materials are removed through lines 16, 17 and 18. The heaviestmaterial which contains all the asphalt and lubricating oil componentsis withdrawn from second crude unit 13 through line 19 and passed tosecond extraction zone 20 wherein it is contacted with a first solventselective for the extraction of the more aromatic and naphtheniccomponents and a second solvent which causes rejection of the asphaltinto the extract or heavier phase. The first solvent, which entersthrough line 21, may be furfural, phenol, or other commonly knownsimilar materials. The second solvent, which enters through line 22, maybe propane, butane, or other light paraffin. The major portion of thelubricating oil components, along with the major portion of the secondsolvent, is removed overhead through line 23 and passed to furtherprocessing, not herein shown.

The extracted materials, along with the solvents and asphalt, whichaltogether comprise the alsphaltic extract, are removed from secondextraction zone 20 through line 24 and are passed into first extractionzone 12 wherein they contact the maltene fraction. For final controlpurposes, it may be desirable to add fresh selective solvent to zone 12through line 25 to aid in removing substantially the last traces of thearomatic and naphthenic materials. Similarly, it may be desirable to addfresh parafiinic solvent through line 26 to promote complete separationof the parafiinic materials which may have been carried over from secondextraction zone 20. Water may be added to zone 12 through line 27 toraise the miscibility temperature of the solvent system and to assist inthe separation of additional paraifinic type oil. Optionally, a smallamount of cycle oil from a downstream catalytic cracker may also beadded to zone 12 through line 28 in a manner which will be more fullydescribed in the discussion of FIGURE 2.

In first extraction zone 12, the combined materials separate into twofractions: a more parafiinic fraction suitable for use as a catalyticcracking stock and a more aromatic fraction suitable for processing ashereinafter described. The presence of the asphaltic extract from thesecond extraction zone promotes simultaneous demetallizing by extractionof the organo-metallic compounds so that the predominantly parafi'inicfraction is improved in its characteristics as a catalytic crackingstock in that it contains less than 25 ppm. of metals. This low metalcontent, more parafiinic material is removed along with a portion of thecombined solvents through line 29. The solvents are separated in zone30, removed through line 31 and may be recycled by means not shown forreuse in the various processing zones of this invention. Thesolvent-free, more parafiinic material is passed on through line 32 forfurther processing, preferably of the type described hereinafter in thediscussion of FIGURE 2.

The predominantly aromatic fraction, which contains the remainingmetals, is Withdrawn from zone 12 through line 33 along with theremaining solvents. The solvents are separated in Zone 34, removedthrough line 35 and may be recycled through means not shown for reuse inthe various processing zones of the invention. The solvent-free,metals-containing, more aromatic fraction is passed on through line 36for further processing in the manner described hereinafter.

The process of this invention is characterized in narrower form by thesuccessive steps also shown in FIG- URE 1. After the processingdescribed above, the solventfree, metals-containing, predominantlyaromatic fraction recovered from first extraction zone 12 is passedthrough line 36 to visbreaking zone 37 wherein mild thermal cracking ofthe heavy materials occurs. The partially thermally cracked efiuent ofvisbreaking zone 37 is passed through line 38 to fractionation zone 3?wherein the lighter materials are separated into at least two fractionsand are removed into a plurality of lines, such as lines 48 and 41. Thepreferred further processing of these fractions is described hereinafterin the discussion of FIG- URE 2. The remaining heavy, visbroken, morearomatic material is withdrawn from the bottom of fractionation zone 39through line 42 and passed into vacuum pitch stripping zone 43 whereinadditional matelials are separated. These materials, such as aparticularly high-quality carbon black oil and pitch binder base stock,are removed through a plurality of lines, such as 44 and 45.

The remaining heavy material, which now comprises predominantlyundesirable asphalts and metals, is withdrawn from zone 43 through line46. If necessary, the pitch binder base stock may be oxidized and/orheat treated to meet designated specifications. in addition, colloidalcarbon in an amount not exceeding 15 weight percent of the pitch binderbase stock may be added to line 45 by conventional means not shown.Preferably, however, the heavy material is passed into partial oxidationzone 47. The asphaltene fraction from deasphaltening zone 8, which hasbeen withdrawn from that zone through line 10, is also passed intopartial oxidation zone 4-7. The combined materials are then reacted inthe presence of oxygen to produce hydrogen which is withdrawn throughline 48. If desired, all or a portion of the heavy bottoms from vacuumpitch stripping zone 43 may be withdrawn from line 46 through line 49and passed to further processing, such as fluid or delayed coking. Themetals may be recovered from the fly ash resulting from combustion ofthe coke; for instance, as a power plant fuel.

The deasphaltening zone may be a batch operation, a multiple vesseloperation or preferably a substantially continuous liquid-liquidcountercurrent treating operation. The residuum to be deasphaltened isgenerally introduced near the bottom of the deasphaltening tower andflowed therein in countercurrent liquid-liquid contact with a suitabledeasphaltening solvent. The solvent used in this process may be any oneor more of the C -C parafiins, such as propane, isobutane, n-pentane,isooctane, cyclohexane or methylcyclopentane. The heavier paraffins arepreferred for they produce higher yields of the deasphalted maltenes. Ina multiple vessel operation, different solvents may be used in differentvessels.

The deasphaltening operation is carried out at any suitabledeasphaltening temperature and pressure. The temperature and pressureare adjusted so as to maintain the deasphaltening solvent in the liquidphase during the deasphaltening operation. A deasphaltening temperaturein the range of 125-600 F., usually not more than 75 lower than thecritical temperature of the deasphaltening solvent, and a pressure inthe range of 200l,000 p.s.i.g. are employed depending on the compositionof the deasphaltening solvent and the composition of the residuumundergoing deasphaltening. The solventto-re siduum' volume ratio is inthe range of 2:1 to 10:1. The deasphaltening tower may be operatedisothermally or under a temperature gradient with the top towertemperature lower than the bottom tower temperature but not more thanabout 75 F. If the residuum is deasphaltened in a series of towers, theabove considerations apply to each tower in the series with, of course,appropriate adjustments in operating conditions for the changingcomposition of the material being treated and the solvent being used ineach tower.

All or part of the solvents used in the deasphaltening zone may beremoved from either or both the maltene and asphaltene fractions byconventional solvent removal means before further processing of thefractions, but this solvent removal is not required. Any solventremaining in the maltene fraction will aid in the paraifinic-aromaticseparation in the first extraction zone and will be removed from theproducts of that zone by the solvent removal operations heretoforedescribed.

The first extraction zone is a vessel suitable for liquidliquidcontacting between the maltene fraction from the deasphalting zone andthe asphaltic extract from the second extraction zone. Preferably, it isa vessel suitable for effecting continuous countercurrent liquid-liquidcontacting. The zone is operated at a temperature in the range oflO0-350 F. and a pressure in the range of 800 p.s.i.g. The temperatureand pressure are adjusted to maintain all the materials in the liquidphase during contacting. Operation may be isothermal; but, preferably,there will be a temperature gradient with the region at the top of thevessel no more than 100 F. hotter than that at the bottom. Preferablythe extract from the second extraction zone enters the first extractionzone near the top of the latter and descends while contacting themaltene fraction from the deasphaltening zone which entered nearer thebottom of the first extraction zone. Any additional streams, such asthose supplyin additional selective solvent or paratfinic solvent orsimilar substitutes for either or both of these, or water, may be addedto the zone by conventional means and at easily determined appropriatepoints in the vessel. It may also be desirable to add some heavy gas oilor other nonasphaltic heavy oil, such as FCC cycle oil, in order toincrease overall product yields when the process of this invention isintegrated into an overall refining processing scheme.

The second extraction zone may be any conventional type of lubricatingoil extract apparatus, such as a single vessel, for extracting a longresiduum, or a plurality of vessels, each extractin a narrow cut fromdistillation of crude oil, followed by blending of the extracts fromeach narrow cut. The principal requirement as far as the process of thisinvention is concerned is that the asphaltic extract from the secondextraction zone contain at least the asphaitic materials and a portionof the selective solvent from the extract. This means that when multiplevessel extraction is used, the extract and at least a portion of thesolvent from the extraction of the heaviest narrow cut will comprise thematerials termed asphaltic extract passed to the first extraction zone.Extracts and solvents from the extraction of one or more of the lighter,narrow cuts may also be included among the materials passed to the firstextraction zone.

FIGURE 2 illustrates an example of the process of this inventionintegrated into an overall refinery processing scheme. The crude to betreated, which comprises 164,000 b.p.d. of a 21.5 API Los Angeles BasinCalifornia crude, enters first crude unit 2 through line 1 and isseparated into five fractions. The lightest fraction is removed throughline 3 and passed to separation zone 50 wherein it is separated into 935b.p.d. of C EFO (equivalent fuel oil), which is removed through line 51,and 3,850 b.p.d. of C to 200 F. light, straight-run gasoline, which isremoved through line 52. From the upper portion of the crudedistillation column, 15,400 b.p.d. of 200-350 F. heavy, straight-rungasoline is withdrawn through line 4. This material is joined withsimilar material from second crude distillation unit 13 and is passed tocatalytic reforming as hereinafter described. At an intermediate pointin the distillation column, 8,950 b.p.d. of 350- 525 F. jet fuel iswithdrawn through line 5. From the lower portion of the column, 7,000b.p.d. of 525 600 F. diesel fuel is withdrawn through line 6. Theremaining heavy material is withdrawn from the bottom of the crude unitand is passed through line 7 to separation zone 53 wherein there areseparated under vacuum 77,765 b.p.d. of 600-1,025 F. gas oil which areremoved through line 54 and passed, after being joined with similarmaterial from second crude distillation zone 13, to subsequenthydro-cracking, hereinafter described. The remaining material amountingto 50,000 b.p.d. of 52 API, 1,025 F.+ residuum containing 180 p.p.m. ofnickel, 175 p.p.m. of vanadium and 100 p.p.m. of iron is withdrawn fromseparation zone 53 and passed to deasphaltening zone 8 through line 55.

Separation zone 53 comprises conventional apparatus suitable forseparation of the heavy bottoms material from the first crude unit intothe gas oil fraction and the heavier residual fraction. It is preferredthat the apparatus be operated under a vacuum.

Deasphaltening zone 8 is operated with a temperature gradient of 50 F.The solvent, 2,757,500 lb./hr. of npentane, is introduced through line 9near the bottom of the deasphaltening column where the columntemperature is 300 F. and contacts the residuum countercurrently. Themaltene fraction is removed overhead from the column through line 11along with the major portion of the n-pentane solvent. The asphaltenefraction is Withdrawn from the bottom of the column along with a minorportion of the n-pentane solvent through line 10. The solvent andmaltene fraction are separated in zone 56, and the separated solvent isrecycled through line 9 to the deasphaltening zone. Additional make-upsolvent may be added to line 9 through line 57 if necessary. Aftersolvent removal, 37,500 b.p.d. of the solvent-free maltene fraction witha gravity of 8.7 API and containing 100 p.p.m. of nickel, 58 p.p.m. ofvanadium and 30 p.p.m. of iron are passed through line 58 to firstextraction zone 12. The asphaltene fraction and solvent may be separatedin zone 59. The asphaltene fraction and solvent may be separated in zone59, and the separated solvent is recycled through line 60 to line 9 anddeasphaltening zone 8. Twelve thousand five hundred b.p.d. of thesolvent-free asphaltene fraction with a gravity of 4.2 API a softeningpoint of 380 F. (as measured by the ball-and-ring method of ASTM D3626)and containing 68.8 weight percent asphaltenes are withdrawn throughline 61 and passed to partial oxidation zone 47.

The asphaltic extract to be used as the demetallizing agent comes from asecond crude oil. Fifty thousand b.p.d. of asphalt-containing crude oil,segregated for recovery of its superior lube oil base stock components,a 33.0 API mixture of San Joaquin Valley California crude and FourCorners Utah crude, are passed into second crude unit 13 through line14. In crude unit 13, the

crude is separated into a plurality of fractions. The lightest fractionis withdrawn overhead through line 15 and is passed to stabilizer 62wherein it is separated into 700 b.p.d. of C EFO, which are withdrawnthrough line 63, and 3,700 b.p.d. of C to 200 F. light straight-rungasoline, which are withdrawn through line 64. Near the top of crudeunit 13, 6,600 b.p.d. of 200-350 F. heavy straight-run gasoline arewithdrawn through line 16. The material is joined with similar materialwithdrawn from first crude unit 2 through line 4 and is passed tocatalytic reforming through line 65 as hereinafter described. At anintermediate point in the crude unit 13, 12,050 b.p.d. of 350525 F. jetfuel are withdrawn through line 17. Near the'bottom of crude unit 13,3,260 b.p.d. of 525 600" F. diesel fuel are withdrawn through line 18.The asphalt-containing heavy bottoms is withdrawn from the bottom ofcrude unit 13 through line 19 and is passed to separation zone 66, whichcomprises a vacuum distillation column, wherein 8,890 b.p.d. of 600725F. as oil are separated. This gas oil is withdrawn through line 67 andis blended with the gas oil from separation zone 53. The combined gasoil streams are then passed to hydrocracking, hereinafter described,through line 68.

Through line 69, 14,800 b.p.d. of asphalt-containing 725 F.+ residuumwith a gravity of 16.5 API are Withdrawn from zone 66 and passed tosecond extraction zone 20 wherein they are contacted with 541,160 poundsper hour of phenol, which enters through line 21, and 344,000 pounds perhour of propane which enters through line 22. A high-quality lubricatingoil is withdrawn through line 23. The stream being withdrawn throughline 23 contains 7,030 b.p.d. of the lubricating oil with a gravity of299 API and a metals content of 0.09 p.p.m. nickel, 0.04 p.p.m.vanadium, 0.46 p.p.m. sodium and 0.16 p.p.m. iron, along with 193,400pounds per hour of propane and 64,000 pounds per hour of phenol. Thephenol and propane are separated from the lubricating oil byconventional solvent removal means not shown.

The remaining material in zone 20 is termed the asphaltic extract andcomprises 7,770 b.p.d. of an extract oil with a gravity of 61 API andcontaining asphalt, 30 p.p.m. nickel, 14 p.p.m. vanadium, 25 p.p.m. ofsodium and 12 p.p.m. .of iron, along with 477,160 pounds per hour ofphenol and 150,600 pounds per hour of propane. This extract is withdrawnthrough line 24 and passed to first extraction zone 12.

The asphaltic extract enters zone 12 near the top and passes downward,contacting the maltenes which have entered nearer the bottom and areflowing upward. The top column temperature is maintained at 160 F. andthe bottom column temperature at F. The pressure is 300 p.s.i.g. Fiftythousand pounds per hour of anhydrous phenol are added through line 25,100,000 pounds per hour of propane are added through line 26, and 25,000pounds per hour of water are added through line 27. Ten thousand b.p.d.of 750 950 F. FCC cycle oil, which may include small amounts .ofcatalyst fines and other foreign material, are withdrawn from the bottomof an FCC unit, hereinafter described, and passed into zone 12 throughline 28. The products of zone 12 are an overhead fraction whichcomprises 43,050 b.p.d. of a more parafiinic raffinate oil (whichcontains 7 p.p.m. nickel, 3 p.p.m. vanadium, 1 p.p.m. sodium and 2 ppm.iron), 5,000 pounds per hour of water, 62,000 pounds per hour of phenoland 141,000 pounds per hour of propane; and a bottoms fraction whichcomprises 12,220 b.p.d. of a predominantly aromatic extract oil, 445,160pounds per hour of phenol, 109,600 pounds per hour of propane and 20,000pounds per hour of water. The parafiinic fraction is withdrawn overheadthrough line 29 and passed to solvent separation zone 30 wherein thewater, propane and phenol are separated by conventional means andwithdrawn through line 31. If desired, the materials withdrawn throughline 31 may be separated and recycled by means not shown for use insecond extraction zone 20 or first extraction zone 12. The solvent-free,predominantly parafiinic .oil, which has a gravity of 129 API, is passedthrough line 32 into first hydrocracking zone 70. The aromatic bottomsfraction is withdrawn from zone 12 through line 33 and is passed tosolvent separation zone 3 wherein the phenol, water and propane areseparated by conventional means and withdrawn through line 35. Thesematerials may be separated and recycled in the same manner as describedfor the materials withdrawn from zone 39 through line 31.

The solvent-free aromatic oil, which has a gravity of 4.7 API, iswithdrawn from zone 34 through line 36 and passed to visbreaking zone37. Zone 37 is a conventional once-through, thermal visbreaking zonecomprising a tubular reaction zone which is operated at a temperature inthe range of 890-910 F. and a pressure of 200 p.s.i. g. to produce mildcracking of the heavy aromatic oil, thus concentrating the aromaticcontent still further by cracking out the nonaromatic material, and aquenching zone wherein the visbroken material is quenched to atemperature of 775 F. and the pressure is reduced to 100 p.s.i.g. Thismaterial is then passed through line 38 into separator 39 wherein it isseparated into three fractions. The lightest fraction, which comprises3,220 b.p.d. of 400 F. materials, is withdrawn overhead through line 40and passed to separator 71 wherein it is separated into 1,220 b.p.d. ofC materials and 2,000 b.p.d. of C to 400 F. catalytic reformer feed. TheC material is withdrawn through line 72 and is recovered or passed forfurther processing by means not shown. The catalytic reformer feed iswithdrawn through line 73 and passed to the first stage of catalyticreformer zone 74, hereinafter described. At an intermediate point inseparation zone 39, 2,000 b.p.d. of 400650 F. hydrocracker feed arewithdrawn through line 41 and passed to first hydro cracking zone 70.The remaining material, which comprises 7,470 b.p.d. of 650 F.+ highlyaromatic materials, is withdrawn through line 4-2 and passed to vacuumpitch stripping zone 43 wherein it is separated by contact with steamwhich enters zone 43 through line 75 into 2,500 b.p.d. of 650-850 F.carbon black oil, 2,480 b.p.d. of 850-1,050 F. pitch binder base stockand 2,490 b.p.d. of l,050 F.+ heavy bottoms material. The carbon blackoil is withdrawn through line 44 and recovered by conventional means notshown. The pitch binder base stock is withdrawn through line 45 andsimilarly recovered, and the heavy bottoms material is withdrawn throughline 46 and passed to partial oxidation zone 47.

Partial oxidation zone 47 is a conventional unit comprising at least agas generator, a shift converter and CO removal facilities. The heavymaterials, which enter through lines 46 and 61, are heated and reactedwith a stoichiometric deficiency of oxygen, which enters through line'76, forming a C-H rich gas which is shift converted to produce 230 ifSCFD of high-purity hydrogen. This hydrogen is withdrawn through line 48and is passed through means not shown to various hydrogen-consumingunits in the system. Metallic contaminants and other ash, which are notconverted to hydrogen, carbon monoxide or carbon dioxide, are removedfrom partial oxidation zone 47 through line 77. Where the initial crudebeing treated contains a large amount of metals, it may be economicallydesirable to recover the metals from the ash by conventional means notshown.

The solvent-free paraifinic material in line 32 and the 400 650 F.visbroken material in line 41 are passed into first hydrocracking zone70 wherein they are contacted with hydrogen and a sulfactivehydrogenation catalyst at elevated temperature of 700-900 F. andpressure of 1,500-4,000 p.s.i.g. The hydrocracking zone serves to removesubstantially all the remaining metal contaminants and to convert atleast 30 percent of the 900 F.+ oil to material boiling below 900 F.Suitable catalysts for use in zone 70 include the sulfactivehydrogenation catalysts of no more than moderate acidity, comprisingcombinations of Group VI and Group VIII metals, their oxides and theirsulfides, especially nickel sulfide together with molybdenum sulfide ortungsten sulfide, associated with an inorganic refractory oxide carrier,such as alumina, silica-alumina, silica-magnesia, and the like. Stronglyacidic hydrocracking catalysts, such as those comprising Group VIIImetals, their oxides and sulfides, associated with an activesilica-alumina cracking catalyst carrier wherein silica is a majorcomponent, are not suitable because they rapidly lose their activity anddo not exhibit sufiicient hydrogenation activity at the conditionsemployed. Hydrogen in an amount of 64 H SCFD is added to zone 70 throughline 7 8. This hydrogen may be supplied from partial oxidation zone 47,catalytic reformer zone 74, or any other hydrogen source. Thehydrocracked oil is passed through line 79 to separation zone 80 whereinit is separated into t ree principal fractions. The lightest fraction,which comprises 430 b.p.d. of mixed butanes is withdrawn overheadthrough line 81. At an intermediate point in separator 80, 2,115 b.p.d.of C to 370 F. reformer feed is withdrawn through line 82 and passed tothe second stage of reforming zone 74. The remaining heavy hydrocrackedmaterial, which comprises 45,070 b.p.d. of 370-850 F. material, iswithdrawn from the bottom of separator 80 and passed through line 83 tocatalytic cracking zone 84.

The 86,555 b.p.d. straight-run gas oil separated in zones 53 and 66 ispassed into second hydrocracking zone 85 through line 68. Secondhydrocracker zone 85 comprises a denitrification stage and ahydrocracking stage. In the denitrification stage, the feed to thehydrocracking process is contacted with hydrogen in the presence of asuitable hydrogenation catalyst at elevated temperatures and pressuresto remove nitrogen compounds therefrom. A particularly effectivecatalyst for removing nitrogen by hydrogenation is one wherein acoprecipitated molybdenaalumina material (e.g., one prepared inaccordance with the disclosure of US. Patent No. 2,432,286 to Claussenet a1. or US. Patent No. 2,697,066 to Sieg) is combined with cobaltoxide, the final catalyst having a metals content equivalent to about 2percent cobalt and 7 percent molybdenurn. Other suitable catalystsinclude those mentioned in the previous paragraph. Representativeprocessing conditions for removing nitrogen with this catalyst are anLHSV of 1-3, temperature of about 700850 F., pressure of about 2003,000p.s.i.g. and l,000l5,000 s.c.f. of hydrogen per barrel of feedstock.

The resulting efliuent is treated in accordance with methods presentlyknown in the art so as to remove ammonia and some hydrogen sulfide whichmay be present. A preferred removal method involves injecting water intothe total efiluent from the hydrofining unit and then passing theresulting mixture into a high-pressure separator operating under suchconditions of temperature and pressure (for example, F. and 950p.s.i.g.) that a gaseous overhead is removed that is predominantlyhydrogen, but which normally contains some hydrogen sulfide and lighthydrocarbons. This overhead (following a clean-up treatment to removeany nitrogen and sulfur-containing compounds, if desired) can berecycled to the denitrification unit along with make-up hydrogen. Twoliquid phases are formed in the separator, an upper hydrocarbon phaseand a lower aqueous phase which contains essentially all of the ammoniapresent and some hydrogen sulfide in the form of ammonium sulfide. Theaqueous phase is removed from the system and discarded.

The hydrocarbon layer is then preferably passed into a stripper ordistillation column from which any remaining hydrogen sulfide, ammoniaand water are removed overhead. The stream may also be freed of anylight hydrocarbon fractions (boiling in the gasoline range or below)formed as a result of hydrocracking reactions taking place over thehydrofining catalyst.

The portion of the denitrified feed to be hydrocracked, along with fromabout 1,SO030,000, and preferably from 1. 1 about 3,000-15,000, standardcubic feet (s.c.f.) of hydrogen per barrel of total reaction feed, ispassed into the hydrocracking zone at a liquid hourly space velocity(LHSV) of from about 0.2 to 15, and preferably from about 0.4 to 3.0,and intimately contacted with the catalyst.

The catalyst employed in the hydrocracking zone is one wherein amaterial having hydrogenating-dehydrogenating activity is deposited orotherwise disposed on an active cracking catalyst support The crackingcomponent may comprise any one or more of such acidic materials assilica-alumina, silica-magnesia, silica-aluminazirconia composites,alumina-boria, fiuorided composites, and the like, as well as variousacid-treated clays, zeolites, and similar materials. Thehydrogenating-dehydrogenating components of the catalyst can be selectedfrom any one or more of the various groups VI, VII and VIII metals, aswell as the oxides and sulfides thereof, alone or together withpromoters and stabilizers that may have by themselves small catalyticeifect, representative materials being the oxides and sulfides ofmolybdenum, tungsten, vanadium, chromium, and the like, as well as ofmetals, such as iron, nickel, cobalt and platinum. If desired, more thanone hydrogenating-dehydrogenating component can be present; and goodresults may be obtained with catalysts containing composites of two ormore of the oxides of molybdenum, cobalt, chromium, tin and zinc, andwith mixtures of said oxides with fluorine. The amount of thehydrogenating-dehydrogenating component present can be varied withinrelatively wide limits of from about 0.530 percent based on the weightof the entire catalyst.

The contacting step is conducted under a pressure of at least 500p.s.i.g., and preferably from about 8003,000 p.s.i.g. The temperature ispreferably maintained in the range of from about 400-750 F.; because, attemperatures above about 750800 F., the amount of gasoline product lostto the less desirable C and lighter materials rapidly increases, thuslowering the motor fuel yield. For example, it has been found that theamount of methane produced at 800 F. per unit of converted product isapproximately sixteen times as great as that formed at 700 F. and fourtimes as great as that produced at 750 F. At higher temperatures, thesituation becomes much worse. With operation at 800 F. and higher withthe same and similar feeds, but with nickel sulfide on silica-alumina,regeneration is required after on-stream periods of a few hundred hoursor less, compared with operation below 700 F., with which can beobtained onstream periods of several thousand hours withoutregeneration. In the present process, it is recommended that thereaction be conducted at an initial on-stream temperature from about500-650 E, with a progressive increase to about 750 P. so as to maintaincatalyst activity at a controlled level. The initial and terminaltemperatures will vary, with character of feed and catalyst, within theoverall range specified above.

Total hydrogen required to process the gas oil is 200 IE SCFD, which maybe supplied through line 86 from partial oxidation zone 47, catalyticreformer 74, or any other hydrogen source. The hydrocracked materialfrom second hydrocracking zone 85 is withdrawn through line 87 andpassed to separation zone 88 wherein it is separated into fourfractions. The lightest fraction, which comprises 16,800 b.p.d. of Cmaterial is withdrawn overhead through line 89. A second fractioncomprising 25,000 b.p.d. of C to 180 F. gasoline is withdrawn throughline 90. The heaviest fraction comprising 10,000 b.p.d. of 390-525 F.material is withdrawn from the bottom of zone 88 through line 01. Afourth fraction, comprising 50,500 b.p.d. of l80390 F. material, iswithdrawn from the lower portion of zone 88 through line 92 and ispassed into splitter 93 wherein it is separated into two fractions. Thelighter fraction, comprising 37,500 b.p.d. of 180320 F. material, iswithdrawn overhead through line 94 and passed to reforming zone 74. Theheavier fraction, comprising 13,000 b.p.d. of 320390 F. materialcomprising 10 percent paraffins, 65 percent naphthenes and 25 percentaromatics and with a leaded F-l octane number of 70, is withdrawn fromthe bottom of splitter 93 through line 95 and may be withdrawn entirelyor in part from the system through line 96 and recovered by conventionalmeans not shown. However, in this example, this 320390 F. material ispassed through line 97 to line 83 and then to catalytic cracking zone84.

Catalytic reforming zone 74 is a conventional two-stage reformer inwhich the first stage is utilized primarily as an olefin saturation,nitrogenand sulfur-removal unit and the second stage serves as theactual reforming unit. For this reason, the straight-run naphthas fromcrude units 2 and 13, which contain some nitrogen and sulfur, are passedthrough line 65 to first stage 98 of reforming zone 74. Similarly, thenitrogen-, olefinand sulfur-containing visbroken material fromseparation zone 71 is passed through line 73 to first stage 98. Afterremoval of the sulfur and nitrogen and saturation of the olefins, thecombined materials are passed through line 99 to second stage 100 ofreforming zone 74, wherein they are combined with the nitrogenandsulfur-free hydrocracked materials in lines 82 and 94.

The reforming zone is operated at conventional reforming conditionsincluding temperatures of about 700 to about 1,050 E, preferably betweenabout 725 and about 1,000 F. The LHSV will vary between about 0.1 andabout 10, preferably between about 0.5 and 4. The hydrogen pressure willvary between about 100 p.s.i.g'. and about 1,000 p.s.i.g., preferablybetween about 250 and 750 p.s.i.g. The molar ratio of hydrogen tohydrocarbon charge will vary between about 1 and 20, preferably betweenabout 4 and 12.

The reforming operation is carried out in the presence of hydrogen and asuitable reforming catalyst. Such catalysts include the metals andcompounds, such as the oxides and/ or sulfides of the metals of theleft-hand column of Groups VI and VIII of the Periodic Table of theElements. The catalyst compounds can be used alone or on a suitablesupport. Catalysts that comprise platinum or palladium metal depositedon supports, such as alumina, halogen-activated alumina, and the like,are particularly suitable. Silica-alumina, silica-zirconia, and aluminaboria are also suitable.

In tl 1e reforming process, there is net production of 58.4 M SCFD ofhydrogen. This net production of hydrogen may be removed through line101 and used all or in part to supply the hydrogen requirements for thehydrocracking zone.

The reformed, combined materials are withdrawn from second stage 100 ofreforming zone 74 through line 102 and are passed into separator 103,wherein they are separated into a plurality of fractions including 2,460b.p.d. of butane and lighter hydrocarbons and 55,200 b.p.d. of Creformate which has a leaded F1 octane number of 102.55. The butane andlighter hydrocarbon stream are withdrawn through line 104 and arerecovered by conventional means not shown. The C reformate is withdrawnthrough line 105 and is similarly recovered.

Catalytic cracking zone 84 is a conventional catalytic cracking unit.Preferably it is of the well-known fluid bed type or the gas lift orbucket elevator type wherein a cracking catalyst, such as zeolites orsilica-alumina powder or pellets, is continuously circulated between areaction zone and a regeneration zone, using conversion conditions of850-l,100 F. and regeneration conditions of 900l,150 F. at nearatmospheric pressure. The manner of controlling the catalytic crackingprocess, primarily by means of the catalyst circulation rate and feedpreheat temperature, to maintain a balance between the heat released byburning coke from the catalyst in regeneration and the heat absorbed bythe cracking reactions is well known.

The materials which enter zone 84 through lines 83 and 97 are convertedinto cracked materials which are withdrawn through line 106 and passedinto separator 107, wherein they are separated into three fractions. Thelightest, which comprises 11,070 b.p.d. of C materials, is withdrawnoverhead through line 108 and recovered by conventional means not shown.The bulk of the cracked materials, which comprises 39,000 b.p.d. C to430 F. substantially olefin-free materials comprising 60 percentaromatics, percent paraflins and 30 percent naphthenes and having an F-lleaded octane number of 99.5, is withdrawn through line 109 andsimilarly recovered. The remaining material, which comprises 10,000b.p.d. of FCC cycle oil with a gravity of 10.3 API, is withdrawn fromthe bottom of zone 107 and recycled through line 23 to first extractionzone 12.

From the initial 214,000 b.p.d. of crude oil processed, the followingproducts are obtained:

TABLE I Product: Yield (b.p.d., except where noted) C EFO 1,635 Butanesand lighter hydrocarbons 2,890 Gasoline 126,750 Jet fuel 21,000 Dieseloil 1 ,260 Lubricating oil 7,030 Pitch binder base stock 2,480 Carbonblack oil 2,500

Hydrogen 24 fislkfd. net).

It can be seen that this process thus produces a high yield of verydesirable hydrocarbon products with only a small loss to light gases.

The above-described flow system and operating conditions are given forillustrative purposes only. It is apparent that many widely differentembodiments of this invention may be made without departing from thescope and spirit thereof and, therefore, it is not intended to belimited except as indicated in the appended claims.

What is claimed is:

1. A process for the demetal lation of a petroleum oil boiling above 900F. and containing asphaltenes and metalliferons contaminants, whichcomprises:

(a) contacting said oil with a C C paraffinic solvent in adeasphaltening zone under conditions such that said oil is separated insaid deasphaltening zone into an asphaltene fraction comprisingasphaltenes with a ring-and-ball softening point above 300 F. containinga major portion of the metalliferous contaminants and a minor portion ofsaid para'l'finic solvent, and a maltene fraction comprisingnonasphaltene materials and the remainder of said metalliferouscontaminants, withdrawing from said deasphaltening zone said asphaltenef action, and withdrawing from said deasphaltening zone said maltenefraction and passing said maltene fraction to a first extraction zone;

(b) contacting in a second extraction zone a partially asphalteniclubricating oil stock with at least one solvent substantially selectivefor the extraction of aromatic and naphthenic components from said stockand at least one solvent substantially selective for the separation ofasphaltic components from said stock;

(c) withdrawing from said second extraction zone an asphaltic extractcomprising the major portion of said selective solvents, asphalteniccomponents, and a portion of the aromatic and naphthenic oil present insaid stock, passing said asphaltic extract into said first extractionzone, and contacting in said first extraction zone said asphalticextract and said maltene fraction; and

(d) separating said contacted materials in said first extraction zoneinto a predominantly parafiinic fraction containing less than 25 ppm.metalliferous contaminants and a predominantly aromatic fractioncontaining the remainder of said metalliferous contaminants andwithdrawing said parafiinic fraction and said aromatic fractionseparately from said first extraction zone, removing said selectivesolvent from each of said fractions, and recovering separately saidsolvent-free parafiinic fraction and said solvent-free aromaticfraction.

2. The process of claim 1 wherein said solvent-free aromatic fractionwithdrawn from said first extraction zone is thermally cracked in athermal visbreaking zone at a temperature in the range of from about 650F. to about 950 F. and a pressure in the range of from about to about1,000 p.s.i.g.

3. The process of claim 2 wherein the product of said visbreaking zoneis fractionated into a plurality of fractions including a more aromaticfraction, and at least a portion of said more aromatic fraction iscontacted with steam in a pitch stripping zone at less than atmosphericpressure to produce a pitch binder base stock.

4. The process of claim 3 wherein at least a portion of said morearomatic fraction from said visbreaking zone and said asphaltenefraction from said deasphaltening zone are converted to hydrogen byreacting in the presence of oxygen in a partial oxidation zonecomprising at least a gas generator, a shift converter, and carbondioxide removal means.

References Cited UNITED STATES PATENTS 2,800,433 7/1957 Read 208-86HERBERT LEVINE, Primary Examiner.

